// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_VIDEO_DECODER_H_
#define MEDIA_BASE_VIDEO_DECODER_H_

#include <string>

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/base/decode_status.h"
#include "media/base/media_export.h"
#include "media/base/pipeline_status.h"
#include "ui/gfx/geometry/size.h"

namespace media {

class CdmContext;
class DecoderBuffer;
class VideoDecoderConfig;
class VideoFrame;

class MEDIA_EXPORT VideoDecoder {
public:
    // Callback for VideoDecoder initialization.
    typedef base::Callback<void(bool success)> InitCB;

    // Callback for VideoDecoder to return a decoded frame whenever it becomes
    // available. Only non-EOS frames should be returned via this callback.
    typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> OutputCB;

    // Callback type for Decode(). Called after the decoder has completed decoding
    // corresponding DecoderBuffer, indicating that it's ready to accept another
    // buffer to decode.
    typedef base::Callback<void(DecodeStatus)> DecodeCB;

    VideoDecoder();

    // Fires any pending callbacks, stops and destroys the decoder.
    // Note: Since this is a destructor, |this| will be destroyed after this call.
    // Make sure the callbacks fired from this call doesn't post any task that
    // depends on |this|.
    virtual ~VideoDecoder();

    // Returns the name of the decoder for logging purpose.
    virtual std::string GetDisplayName() const = 0;

    // Initializes a VideoDecoder with the given |config|, executing the
    // |init_cb| upon completion. |output_cb| is called for each output frame
    // decoded by Decode().
    //
    // If |low_delay| is true then the decoder is not allowed to queue frames,
    // except for out-of-order frames, i.e. if the next frame can be returned it
    // must be returned without waiting for Decode() to be called again.
    // Initialization should fail if |low_delay| is true and the decoder cannot
    // satisfy the requirements above.
    //
    // |cdm_context| can be used to handle encrypted buffers. May be null if the
    // stream is not encrypted.
    //
    // Note:
    // 1) The VideoDecoder will be reinitialized if it was initialized before.
    //    Upon reinitialization, all internal buffered frames will be dropped.
    // 2) This method should not be called during pending decode or reset.
    // 3) No VideoDecoder calls should be made before |init_cb| is executed.
    // 4) VideoDecoders should take care to run |output_cb| as soon as the frame
    // is ready (i.e. w/o thread trampolining) since it can strongly affect frame
    // delivery times with high-frame-rate material.  See Decode() for additional
    // notes.
    virtual void Initialize(const VideoDecoderConfig& config,
        bool low_delay,
        CdmContext* cdm_context,
        const InitCB& init_cb,
        const OutputCB& output_cb)
        = 0;

    // Requests a |buffer| to be decoded. The status of the decoder and decoded
    // frame are returned via the provided callback. Some decoders may allow
    // decoding multiple buffers in parallel. Callers should call
    // GetMaxDecodeRequests() to get number of buffers that may be decoded in
    // parallel.
    //
    // Implementations guarantee that the |decode_cb| will not be called from
    // within this method, and that it will be called even if Decode() is never
    // called again.
    //
    // After decoding is finished the decoder calls |output_cb| specified in
    // Initialize() for each decoded frame. |output_cb| may be called before or
    // after |decode_cb|, including before Decode() returns.
    //
    // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
    // |output_cb| must be called for each frame pending in the queue and
    // |decode_cb| must be called after that. Callers will not call Decode()
    // again until after the flush completes.
    virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
        const DecodeCB& decode_cb)
        = 0;

    // Resets decoder state. All pending Decode() requests will be finished or
    // aborted before |closure| is called.
    // Note: No VideoDecoder calls should be made before |closure| is executed.
    virtual void Reset(const base::Closure& closure) = 0;

    // Returns true if the decoder needs bitstream conversion before decoding.
    virtual bool NeedsBitstreamConversion() const;

    // Returns true if the decoder currently has the ability to decode and return
    // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
    // this will always return true. Override and return false for decoders that
    // use a fixed set of VideoFrames for decoding.
    virtual bool CanReadWithoutStalling() const;

    // Returns maximum number of parallel decode requests.
    virtual int GetMaxDecodeRequests() const;

private:
    DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
};

} // namespace media

#endif // MEDIA_BASE_VIDEO_DECODER_H_
